The “Hydrogen Economy” is expected to grow continuously and hydrogen may eventually supplant fossil fuels as a primary energy source for many applications. Numerous hydrogen applications are being developed, including hydrogen-powered fuel cell or internal combustion vehicles, stationary power applications, backup power units, power grid management, power for remote locations, and portable power applications in consumer electronics, business machinery, and recreational equipment. A significant expansion of the Hydrogen Economy will require marked improvements in existing hydrogen delivery systems. Adapting these systems to deliver blends of hydrogen and other compressed gases can be particularly problematic.
When filling a receiving tank with one or more compressed gas streams, the compressed gas streams' flow rates must be controlled and the streams must be well-mixed to prevent the receiving tank from overheating. For example, rapid refueling of a receiving tank with a hydrogen gas stream can cause the internal gas temperature of a receiving tank to rise by about 50° C. due to adiabatic compression of the hydrogen gas stream and the reverse Joule-Thompson (J-T) effect. (Hydrogen and helium are exceptions to the rule that temperature decreases with expansion of the gas, i.e., they exhibit a reverse Joule-Thompson (J-T) effect.)
Overheating is still a concern even though the heat of compression is partially offset by isentropic expansion and resultant cooling within the storage vessel, and proves to be a greater risk with larger tanks.
U.S. Pat. No. 6,786,245 discloses an apparatus and method for controlling the rate of delivery of a pressurized fluid from a storage vessel to a receiving tank through a conduit in fluid communication with the storage vessel and the receiving tank.
U.S. Pat. No. 5,139,002 ('002 Patent) discloses the use of blends of hydrogen and natural gas as vehicular fuels. The '002 Patent also discloses the simultaneous flow of two compressed gas streams through a common gas fitting on a horizontal storage cylinder useful in transportation applications.
U.S. Pat. No. 5,771,948 ('948 Patent) discloses methods and apparatus for dispensing natural gas into the natural gas vehicle cylinder of a motor vehicle. The '948 Patent discloses that changes in the mass of a compressed natural gas stream can be correlated as a function of initial cylinder pressure.
Commonly-owned U.S. patent application Ser. No. 11/247,561 describes systems and processes in which the flow rate of compressed gas from a source to a receiving vessel or tank is controlled to achieve a desired ramp rate.
Individual gaseous stream control valves have been used to provide pre-blending flow control in processes in which two or more gas streams are blended and delivered to a receiving vessel. Alternatively, a control valve has been associated with one component stream and a restricted flow has been imposed on the secondary stream. These approaches suffer from the disadvantage that high pressure control valves are expensive, relatively uncommon, and are often unrated for use with flammable gases.
Accordingly, the need exists for processes and systems that deliver blends of compressed gases to a receiving tank or vessel without causing an unacceptable increase in vessel or tank temperature and without the need for a prolonged fill times.